1. Technical Field
This application relates to surgical apparatus, and more particularly to surgical apparatus having tool structure which can be rotated about a longitudinal axis.
2. Background of Related Art
The function of engaging and deflecting tissue or organs has been conventionally performed by one of several methods. A retractor, ordinarily in the form of a broad paddle or multiple fingers attached to a handle, may carry out this task. See, for example, U.S. Pat. No. 3,467,079 (James). Alternatively, this function may be carried out with a clamp device to grasp and deflect tissue. In order to facilitate access to internal structures it is widely known in the art to provide surgical instruments with articulating, and more particularly, rotating tool portions. It is also well known to provide the rotational feature with detents or other engageable surfaces to provide positive engagement of the tool portion at discrete angular position and inhibit free rotation thereof. However, these rotation inhibiting mechanisms can be subject to disengagement and unintended rotation of the tool portion when attempting to manipulate resistant tissue structures or to lift heavy organs during surgical procedures may result.
Endoscopic or laparoscopic procedures overcome many of the drawbacks of conventional surgery, particularly the requirement of making large incisions, often through major muscle groups, in order to manipulate the instrumentation in the body cavity. In contrast, instruments for use in endoscopic procedures are characterized by the provision of an elongated cannula structure having a relatively small diameter with a proximal and distal end. The distal end is passed through the surrounding tissue into the body cavity via an incision in the body cavity. The cannula provides a conduit for insertion of surgical instrumentation. The smaller incisions necessary for these procedures allow for shorter patient recovery periods and require less anesthesia than conventional methods.
Endoscopic or laparoscopic procedures, while minimizing patient trauma, reduces access to internal organs and therefore requires surgical instruments with tool structure remotely actuatable from outside the body. Typically this remote actuation includes manipulation of tool structure as well as rotation and articulation thereof. Commonly assigned U.S. application Ser. No. 07/925,496 discloses a surgical instrument adapted for rotating and articulating the tool structure relative to the longitudinal axis thereof. In particular, the apparatus shows a mechanism for indexing rotation of the tool structure.
However, for a surgeon performing operative procedures with heavy or resistant tissue structures, sufficient stress on the tool portion may overcome the rotation indexing mechanism and result in unwanted rotation of the tool structure. Therefore, a position locking mechanism is desired to positively fix the angular position of the tool structure against unintended rotation with respect to the handle.